1. Field of the Invention
The invention embodies an agricultural tractor improvement. More specifically a cooling system for a tractor is provided with air intake access on top of the hood and an air discharge through the grille area of the tractor. Separate compartments are provided for the engine and for the various heat exchangers of the tractor with an exhaust duct between the engine compartment and the heat exchanger compartment allowing evacuation of the engine compartment through the use of a radiator fan.
2. Description of the Prior Art
Background patents include but are not limited to U.S. Pat. Nos. 4,086,976, 3,946,824, 2,871,968, and particularly 3,043,390.
Current agricultural tractors are all of a similar straightforward design that has been utilized throughout the development of tractors since the early twentieth century. Two-wheel drive tractors are typically front engine machines having long hood structures extending from the operator's zone at the rear of the vehicle to the front grille. The engine, part of the transmission and most auxiliary operating equipment are housed under the hood. In tractors having water cooled engines the engine coolant heat exchanger and an air flow inducing fan are provided near the front of the vehicle. In most cases the front grille is the intake access to provide a flow of cooling air to the various heat exchangers. Some tractor models have side air intake grilles with air flow being directed through heat exchangers back toward the vehicle engine.
In liquid cooled tractors the engine coolant heat exchanger or more commonly, radiator, is connected by hoses to the engine block. The radiator and the engine are separated by an engine driven fan of a suction type that draws a stream of ambient air through the radiator to allow heat transfer from the radiator to the air stream. The ambient air is heated as it is drawn through the radiator and is then directed, by the circumstances of the conventional layout, over the surfaces of the engine where the air flow further assists in cooling localized hot spots on the engine. This heated air eventually flows outwardly from the engine compartment with flow on the left side of the vehicle directed downwardly and flow on the right side of the vehicle directed upwardly. The heated air impinging on the ground surface will raise dust and chaff under usual farming conditions. Excess ground dust and chaff agitation requires frequent cleaning of cab windows, engine radiators and the air cleaner. The tractor operator is also subjected to this blast of hot air, both from the downwardly directed air flow and the upwardly directed air flow, or if the tractor is equipped with a modern day cab, the exterior of the cab is heated by the heated air; this requires air conditioner capacity tht is greater than need be when compared to the instant invention.
The engine noise, including the noise of ancillary equipment such as the cooling fan, is more critical in these times of high horsepower tractors and environmental concerns. The long term exposure to high noise levels leads to undesirable levels of fatigue. The farmer operating his tractor is exposed to these high noise levels for very long periods of time during peak farming seasons when he may work from sunrise to long after sunset preparing his land for seeding and later when harvestring his crop.
In order to minimize the noise levels on tractors it will be necessary to provide baffles around the engine compartment. This development can be seen in the small lawn tractors now being marketed where the usual hood is augmented with side panels extending down to the frame of the vehicle. This solution is feasible with these small tractors as the typically utilize air-cooled engines in small horsepower sizes. They do not generate the tremendous heat load that a large diesel engine farm tractor generates.
If side sheets were added to contemporary farm tractors for noise attenuation a severe localized engine cooling problem would arise. The engine compartment would still receive a blast of heated air from the radiator fan but the air would have to exhaust out the bottom of the engine compartment. This would lead to two difficulties. First, pockets of heated air would be trapped in the engine enclosure preventing the "washing" of the engine block with the desirable cooling flow of air. This would result in probable engine damage due to overheating. Secondly, all the air being drawn through the radiator would have to escape out under the engine compartment and would cause considerable dust and chaff disturbances which are undesirable.
The large tractors require a large volume of air flow through the radiator to ensure adequate cooling. Cooling system capacity becomes sensitive to wind direction when tractors are operated in long fields where the tractor will be operating with a tail wind for long periods of time. Designed in overcapacity is the norm as field operating conditions dictate that the cooling system operate at a given maximum level of efficiency regardless of wind conditions or vehicle velocity. For instance, when the tractor is traveling directly into the wind the air flow through the radiator is augmented by the differential between the speed of the tractor and the wind speed, therefore head winds often enable cooling to be maximized. On the other hand tail winds, as well as cross winds, do not add velocity to the cooling air flow and the tractor's radiator fan must supply all the required air flow. Thus cooling systems must be designed with this tail wind situation as the minimum cooling performance threshold resulting in overcapacity of the cooling system during approximately half of its operating time.
In view of these disadvantages of the prior art a revised cooling air flow configuration is set forth in this disclosure, with primary emphasis directed to the location of the air intake for the heat exchanger compartment in its strategic respects to double walled side sheets which are provided and to the inlet of an engine air cleaner which is provided.
In other words, the stream of intake air from the screen is directed relative to the radiator compartment immediately to supply the air cleaner inlet and the radiator in common with fresh ambient air, but is so baffled as to be effectively bypassed by another stream of air being simultaneously directed from the engine compartment, through the double walls of the side sheets, thence to the downstream side of the radiator. So joinder of the two coexisting air streams, the former radiatorheated and the latter engine-heated, strategically deferred to a point of confluence downstream of the radiator where they merge and are jointly drawn into the fan and blown in common forwardly out the air discharge port at the front grille provided on the tractor.
Among the objects of this invention is the provision of a cooling system design that provides for the enclosure of the tractor engine compartment with full side panels in order that noise generated in the engine compartment can be partially contained and attenuated. This full engine closure will reduce bypass noise. Noise levels in the operator's area will also be reduced due to the side panels and the reverse flow of the cooling air passing out through the front grille away from the operator's station.
Other advantages realized by utilization of this invention include, but are not limited to, an absence of a fan blast on the ground thereby minimizing dust and chaff agitation and minimize collection of chaff on the inlet screen of the radiators.
An advantage of the intake screen location above the heat exchanger compartment is that the screen is self-cleaning primarily after the engine is shut down thus maximizing air flow to the heat exchangers.
Also a significant advantage of having the screen located above the heat exchanger compartment is that the operator is visually aware of abnormal chaff accumulation on the screen.
The invention provides several cooling system advantages including maximization of cooling system effectiveness as a function of wind direction. Also, with the intake screen covered with ice and/or snow there will be no overheating even at full load as the intake screen is designed to flex thus breaking up any ice formation. The design allows a smooth controlled flow of intake and outlet air as the engine block is not interposed in the path of cooling air flow, but in the path of a separate, bypassing air stream.
The intake screen is advantageously larger than would be possible with the conventional front grille intake vehicle where the grille size is constrained by hood width and height. Baffling as taught according to the present principles affords an otherwise unused room for a forward extension of the intake screen so as to greatly multiply the cross sectional intake area available.
These as well as other advantages will be recognized through an understanding of the drawing figures as described herein which disclose certain preferred embodiments of the invention.